A4 Cabrio 2.5TDI BDG: grauer Rauch bei Kaltstart | Beiträge 64+

I'd also like to suggest the possibility that perhaps too short spark plugs were used. My A2 3L started up fine in the winter, even though the additional ones were all defective after about 150,000 km, but it was still causing me pain in my ears. The spark plugs were about 1.5 cm too short. So, even when they were working, they probably had little impact on starting.

My Allroad 2.5 TDI AKE, on the other hand, started very reluctantly with only 2 functioning spark plugs. It was similar to the video, but in my case, the 2 cylinders with good spark plugs ran smoothly, while the other cylinders took some time to ignite.

Okay, the car was now at the Bosch service (not quite around the corner).
There, my request to remove and inspect the GK was fulfilled, and four rather blackened spark plugs were found in cylinder four.
Whether there was dirt at the sealing point during installation, or whether the plug was simply not tightened correctly, no one knows.

I just need to wait until the engine is completely cold, and then I will report back.

What length or bulb type is suitable?

Yes, that's correct, according to Bosch as well. The model that has now been installed, which was also used by Audi a year ago, is the Beru GN008.

[quote="dieselschrauber"]It would also be possible to have a coolant temperature sensor that only provides incorrect values at cold temperatures, which I have experienced before.[/quote]
Just now, it's so wonderfully cold. Check the coolant temperature that the engine control unit (ECU) sees when the engine is cool, and compare it to the outside temperature.

Best regards, Rainer

Unfortunately, I can't get the car warm today because I need it to get to work. However, it should be fine once the temperature reaches around -2 degrees Celsius and stays at 1.X degrees, as I checked earlier.

Just to be sure: Has the car not been tampered with? If someone with the wrong plates has...

No, nothing has been changed about that car at all, it's just very traditional

Okay, I can report success: it was the mentioned glow plug.

This morning, I started the car, which had been parked outside, at -4°C, and the engine started smoothly and sounded as expected.

There was no smoke produced.

Therefore, it was a glow plug that was not correctly rotated.

So: the issue is resolved, thanks for your help!

Thank you for your feedback!